Photovoltaic (PV) energy generation systems are attractive from the point of view in that they offer a way of generating electricity without CO2 emissions and other drawbacks of conventional energy sources. However, they suffer from the drawback that the best sites for generation are geographically located around the tropics, far from major load centers. For this reason long-distance power transmissions are likely to be necessary if photovoltaics should be employed on a large scale.
For very long distances and subsea transmission the preferred method is currently high voltage direct current (HVDC) transmission. The most intuitive way of creating a PV power plant with HVDC connection is shown in FIG. 1. The plant comprises a large number of PV panels connected in series and parallel to form arrays. These arrays are connected to inverters which convert the unregulated DC output from the PV panels into a regulated AC voltage and ensure that the PV arrays operate in their maximum power point. The inverters feed power into an MV AC collection grid via transformers. The collection grid is connected to a current source converter HVDC converter station, which requires large filters and capacitor banks for compensating the harmonic currents and the reactive power demand associated with the thyristor converter. Also startup of the system provides a technical challenge since there is no large voltage source present in the collection grid, such as a synchronous generator, that can allow for the energizing of the collection grid. One way of mitigating this problem is to provide a STATCOM or a Diesel Gen-set unit in the collection grid. This however, implies cost and power losses that should preferably be avoided.